avz

Phones can easily be oriented either way, unlike most laptop and workstation screens.

Majority of views certainly come from people whose eyes are horizontally next to each other and therefore whose field of view has a greater extent in the horizontal rather than vertical direction.

Admittedly I don't understand where the vertical recording fad comes from. Personally I take pictures and photos that are almost exclusively horizontal except in rare cases like taking a picture of a very tall building.

The US has extended the protection of the law to the law-abiding Irish, Italians, Germans, Russians, Jews, East Asians, Indians, and Latinos freeing them up to flourish and build human capital. By contrast, the same state has not only failed to do so for the Black community, but its agents have engaged in extrajudicial killings of the community's members with impunity since they lost their legal "protection" as someone else's private property.

Community under assault will redirect its private efforts to security which then undermines cultural and economic development and slows down formation of human capital. That's because security needs are fundamental and trump cultural and economic development [1].

Regarding Indian Hindus, Sikhs and Muslims, I disagree they are indistinguishable for outsiders. Typically, anybody who cares can tell by the name, place where they live, or even just the job they do.

[1] https://en.wikipedia.org/wiki/Tulsa_race_massacre

Well, the may have understood the concept of "running out of stuff" and yet not realize it naturally belongs with numbers (of which they would have known other examples like one and two). I can imagine ancient folks putting the notion of "running out of stuff" with ideas such as "hungry", "empty", "dead" etc. Formation of the more abstract concept of zero-the-number is certainly a few cognitive experiences further down a line.

The perspective of modern computer science (with its zero-based indexing etc) or modern algebra (with its need for neutral element for addition) certainly makes it clear that zero is just another integer. However, without those perspectives I doubt it is so obvious.

For example, people normally count things by starting from one, so, at least following this usual procedure, counting to zero is technically speaking impossible. Also, we can't distinguish between zero apples and zero oranges, but we can tell two apples and two oranges apart.

In fact, even with the perspective of modern algebra zero remains special. For example, it is the only element of a field without a multiplicative inverse.

I'd be surprised if zero didn't take any extra effort to discover. It's clearly different than other integers.

The OP said "There's more time between the last Stegosaurus and the first T-Rex" which computes to 145-72 = 73 and "then (sic) there is between the last T-Rex and us right now." which computes to 66-0=66. Note that 7 million years is about 10% of the timescales involved, so perhaps not something to be dismissed as "scientific error".

Agreed. Perhaps the most prominent example of this shameful behavior is this one:

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

Source: https://www.rust-lang.org/tools/install

Technical detail: Having crossed all meridians is generally not considered the proper criterion for circumnavigation since this is trivially done near the poles. The definition I have come across include a loop that partitions Earth's surface into two parts of comparable area.

Looks good to me as a rough back-of-the-envelope calculation to get the orders of magnitude right (the speed will go down as the object is climbing out of Sun's gravity well).

However, you're still missing a guesstimate for alien lifespan. Do you have reasons to believe they live shorter than 33552 Earth years?

Also, is 38 km/s really the top speed for hypothetical interstellar ship?

I imagine aliens that live on average 870 Earth years (~10x average lifespan of a female Japanese) and travel at 9,000 km/s. They can easily make Sun-Proxima Centauri trip six times in a lifetime.

It seems to me that "the universe" is not an appropriate term for our close planetary neighborhood.

There is a difference between an interstellar object passing within 85 times the distance to the Moon (so closer than Mars at closest approach to Earth) and say a supernova thousands or millions of light years away (and hence thousands or millions of years ago).

I don't know where the universe begins, but I'd say Low Earth Orbit and the Moon don't qualify while Proxima Centauri does. For reference:

Distance from ground to space: ~100 km

Distance from California to Australia: ~12,000 km

Distance to the Moon: ~400,000 km

Distance to 'Oumuamua's closest approach: ~33,000,000 km

Distance to Mars at closest approach: ~55,000,000 km

Distance to the Sun: ~150,000,000 km

Distance to Neptune: ~4,500,000,000 km

Current distance to 'Oumuamua ~5,000,000,000 km

Distance to Sedna: ~13,000,000,000 km

Distance to Proxima Centauri: ~40,000,000,000,000 km

Whoever has more weapons get the land.

Aliens might not actually be land-based creatures like us. Those who evolved on planets entirely covered by liquid (water or otherwise) might even find the idea of "land" fairly strange.

(It's actually quite interesting to ponder the stages of discovery that liquid-based intelligent aliens might go through. First they might discover air (and land if available) and only after that space as another outer layer. I suppose that adds extra thrill we didn't have. Supposing of course that conditions there allow gas and liquid to exist as separate phases. Planets above criticality would probably be weirder still? Would any bottom rocks under the supercritical fluid still count as land - as opposed to "sea floor"?)

What does "habitable" mean in the context that includes multiple alien species that evolved independently on different planets? After all, alien fishalikes that might have evolved in the methane lakes on Titan are unlikely to share our idea of "habitable"...

Single planetary system isn't much more of a protection than a single planet against some of the possible extinction events, e.g. ones associated with the activity of the Sun or intelligent aliens.

Humanity has survived for 100s of millions of years without as asteroid annihilating us, and I don't see it changing now).

Homo sapiens is thought to have existed for mere 300,000 years. Our last common ancestor with the chimpanzee [1] existed no more than 13 million years ago. K-T extinction event [2] that wiped out dinosaurs happened 66 million years ago. There have been numerous extinction events before and after that [3].

On the timescales of species this planet isn't safe. At these timescales rare events become regular occurrences.

[1] https://en.wikipedia.org/wiki/Chimpanzee%E2%80%93human_last_...

[2] https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_e...

[3] https://en.wikipedia.org/wiki/List_of_extinction_events

I think the situation with interstellar travel is well summed up in this conversation between TARS and Cooper as they attempt to dock at Endurance (intentional pun hiding in movie title):

TARS: It's not possible.

Cooper: No, it's necessary.

It seems impossible, but if we don't pull it off we die. And I don't mean we the few folks on HN. I mean everyone.

Earth is a graveyard of species. Nearly all (99% IIRC) species that ever existed have gone extinct (most before we showed up). As a species, we can't stay here and live. A 9-mile thin layer of gas over a single small planet is just not a reliable long-term basis of survival. In fact, the fragility of our tiny little habitant is on display right in front of us this century.

I agree with your conclusion, but I always find that these discussions miss the role of medical science.

The key parameters governing feasibility of human interstellar travel are the average human lifespan in years and typical interstellar distance in lightyears. These are roughly 72 years and 5 lightyears, respectively. So it takes about 70% of a human lifespan to travel a typical interstellar distance at 10% of the speed of light. This is... not great.

The key realization is that the relationship of these two numbers is in a sense an accident of biology and astronomy.

It is usually assumed that future technological progress might enable travel at a large fraction of the speed of light, but it is often missed that future medical progress might extend human lifespan to say 400 or 1000 years.

A scarier realization is that intelligent aliens might have natural lifespan that make interstellar travel seem far more practical.

Side note: Sorry to spoil the apparently impeccable record, but for completeness:

A half-century ago, civilians could experience supersonic flight. Well, it has since become impossible.

A half-century ago, people walked on the Moon. And not once since.

Just a reminder then that unfortunately the passage of time alone is insufficient to guarantee technological progress. Now, let's get back to work, I guess...

This made me think of Elephant in Cairo [1] and Pachydermic Personnel Prediction [2]. Specifically, it reminded me of what the classification says about the job of a politician:

Politicians don't hunt elephants, but they will share the elephants you catch with the people who voted for them.

Along these lines, we'd have something like

Europeans don't invent new tech, but they will regulate the tech you invented.

As a fellow European, I struggle to feel any pride or happiness about this.

[1] https://en.wikipedia.org/wiki/Elephant_in_Cairo

[2] https://www-users.york.ac.uk/~ss44/joke/elephant.htm

Why has no human stepped foot on the moon for 50+ years?

Technically, this is not true. Unfortunately, it will be true in a few weeks.

https://en.wikipedia.org/wiki/Apollo_17

This is not unscientific. Since we don't have a single unified and consistent theory of everything, it is very reasonable to suspect that not all laws of physics are known to us now. The quest to uncover the unknown laws is one of the major motivations to do basic scientific research. It is often done at the extremes: extremely high energy, extremely small scale, extremely large scale and many think we should try extremely complex systems of which life is an excellent example. There is absolutely no reason why evolution wouldn't take advantage of physical laws which we don't know or are unable to recognize.

For a random example of a physics article demonstrating such search, see https://physicstoday.scitation.org/doi/10.1063/PT.3.4546

give much more flavor and diversity to the world than what rational thought will ever produce.

I don't know. The religious and mythological concepts such as punishment, judgment, sacrifice, angels, daemons and elves look like a derivative reflection of humans and their society. By comparison, the concepts from science and technology such as force fields, wavefunctions, wormholes and black holes seem genuinely novel and weird.

Personally, I would certainly not give up on the scientific truth - often in conflict with religion and mythology - to enjoy some of that mythological flavor.

No, it still isn't infinite. Under reasonable assumptions the series is actually bounded from above by a geometric series [1] which is famous for having a finite sum when ratio is <1 [2]. In this case, the ratio r=1/(1+i) is indeed <1. More importantly, no asset exists an infinite amount of time, so the sum is actually finite anyway.

Perhaps we should dispose with all the math though as it should be intuitively clear that if we discount future cashflows at zero rate, i.e. if we do not discount future cashflows, then their present value should be equal to the future value. After all, discounting just means that you value future money less than today's money. If you don't discount, you value both the same, so whatever formula for discounting you use it must be true that plugging in zero rate yields NPV equal to the sum of future cashflows.

Agreed about risk discount. Perhaps what you mean by "whippy" is that as the risk-free interest rate goes to zero NPV becomes increasingly sensitive to the risk discount.

[1] https://en.wikipedia.org/wiki/Geometric_series

[2]: See [1]. Also, as an example, recall that 1+1/2+1/4+1/8+...=2.

The Fed has held interest rates at 0 (negative, real terms) which makes all cash flows effectively infinite net present value.

No, it doesn't. Net present value (NPV) of future cashflows is defined [1] as the sum over time periods of the ratio of the cashflow in the k-th period to one plus the discount rate raised to the power of k:

    NPV = sum_k r_k / (1 + i)^k

    NPV = sum_k r_k

[1] https://www.investopedia.com/terms/n/npv.asp

The only one I can think of right now that releases energy when burnt in oxidizing atmosphere is H2, though there almost certainly are others.

Interestingly, if we go in the opposite direction we also loose something:

Real numbers (1-dimensional): No more algebraic closure [1]

though as you suggest we do gain a nice ordering where "nice" means "compatible with operations". BTW, you can always impose some ordering on all of these sets. It is the orderings' compatibility with arithmetic that we lose going from real numbers to complex numbers.

This can be generalized a little. Real numbers fail to be algebraically closed because some real polynomials lack real solutions, e.g. xx=-2. Complex numbers "fix" this problem since there every n degree polynomial has exactly n roots (counting multiplicity). In a sense, quaternions overdo this, e.g. xx=-2 has an infinite number of solutions (exercise for the reader). However, since quaternion multiplication is not commutative, polynomials as traditionally understood are ill-defined. For example, axx, xax and xxa are different degree two quaternion "polynomials". Ugh.

[1] https://en.wikipedia.org/wiki/Algebraically_closed_field

QKD has a number of fairly well-known limitations:

* It suffers from a built-in vulnerability to denial-of-service attacks because eavesdropping destroys quantum information.

* It lacks an authentication mechanism and is vulnerable to MITM. In practice, classical protocols are used to add authentication and to protect against MITM.

* It is a hardware solution and thus expensive to deploy, upgrade and maintain.

At the same time, contrary to the usual claims of "security guaranteed by the laws of physics", its security is limited by the security of non-quantum elements of the implementation. IOW, the usual reference to the no-cloning theorem for quantum information is irrelevant because QKD uses both quantum and classical information and the latter is clonable and therefore implementations suffer from side channel leaks.

Thus, QKD is an expensive and impractical solution to a problem already solved robustly and cheaply by classical protocols. Hopefully, the hype around it fizzles out before it harms related fields with an actual promise, such as quantum computing.

The paper describes a design for a linear accelerator that would reach 250GeV in center of mass frame and that may be extended to 550GeV (see section 2) and even multi-TeV (see section 5).

I was curious how this compares against LHC which Wikipedia [1] says reached record 13TeV total collision energy. However, it isn't clear whether Wikipedia cites energy in center of mass frame that could be directly compared.

Does anyone know how the two accelerators would compare in this respect? In particular, would the proposed C³ accelerator actually achieve higher total collision energy than LHC or is it instead hoped that future extensions of a C³ accelerator would exceed LHC's capabilities?

[1] https://en.wikipedia.org/wiki/Large_Hadron_Collider

Prices increase when you have a shortage. Prices decrease when you have a surplus. We can maintain prices by growing housing stock in line with population. (The same applies to everything else from semiconductors to cars to human labor.)

In California, people used zoning regulations to create a shortage and predictably house prices rose. Some people got richer. Other people got evicted.

Ideally, we'd create a slight housing surplus to reduce prices. As an added benefit, this would reduce rent-seeking opportunities and create a buffer of empty housing stock that would make moving and searching for a new place to live less of a hassle increasing people's mobility.

In a hypothetical world where humans eat something durable like wood, making wood an investment would create a group of people who cannot afford food.

In the real world where shelter is durable, making it an investment creates a group of people who cannot afford shelter.

Homeownership-as-investment is a mechanism to increase one's wealth at the expense of the less fortunate. It is ethically bankrupt.

It is also a disgrace that even though technological progress makes more and more things people need affordable, we use political means like zoning regulations to artificially drive up home prices in order to turn them into a good investment and thus unaffordable for some.

the creator should be defined as the entity that paid...

No. The existing definition of "creator" as the person who did the creating is perfectly fine. Various supporters, such as those who provided the creator with lodging, food, salary or other provisions are themselves not the creator.

If you pay an engineer to create a psidget, you haven't created anything. The engineer did. You simply exchanged your money for the engineer's creation. This is similar to how paying a farmer for their crops does not turn you into a farmer.

not the engineer / tools that were used to create

Do not conflate people and tools.

In some cases, people will pay you for making things that help them hurt or exploit other people. It could be argued that this constitutes making the world a worse place.

For example, you could get paid by criminals to make ransomware or by an ad company to flood users with ads or by a cryptocurrency company for building tools that facilitate money laundering and tax evasion or by a government to create a database of dissidents and protesters or by a toy company to use ML to generate fake reviews...

If suffering is a problem to solve, then so is death. This is evident to all who grieved.