Light comes in different wavelengths. If you collect light in at least 3 different wavelengths, you have "color" as the human eye/brain knows it. If you want it to match what our eyes see, you collect light at the same three parts of the EM spectrum that the three different color sensors in our eye are sensitive to.

The reason for them giving off different amounts of light in different wavelengths is that different molecules and atoms emit, absorb, and scatter light differently. Things of different temperatures also give off different wavelengths of light. All of which can be collected and assigned to one of the axes of the color space of an image.

> Under the laws of special relativity an observer in a space ship travelling at 0.1c will see Earth speed up, while an observer on Earth will see the ship slow down.

No they won't. They'll both see each other slow down, since motion is truly relative. From the perspective of the Earth, the ship is moving away. From the perspective of the ship, the Earth is moving away. Neither is right or wrong. Both see symmetrical time dilation.

The unintuitiveness of this fact is why the twin paradox is so famous, despite not really being a paradox: https://en.wikipedia.org/wiki/Twin_paradox

We've even already gone through the process of predicting a dark particle that does not interact with the strong or electromagnetic forces to make an equation add up, and then waiting 35 years to be able to have a single detection of that particle. Neutrinos are "dark matter", we just don't call them that because we know that they're too hot and light to be responsible for the features of the universe that the term "dark matter" was coined as a placeholder name for.

m - M = -5 + 5 Log (d)

where:

m = apparent magnitude
M = absolute magnitude
d = distance measured in parsecs

Middle school algebra to check.

It's called a "hypothetical question". One asked not to gain information, but, in this case, to cause the reader to question an assumption that they have already made. This is a pretty simple concept.

> Antimatter has nothing to do with dark matter

"Nothing to do with" is a pretty strong assertion. How'd you come to that conclusion? And what makes you so confident in it that you feel the need to present it as fact to people?

https://www.nature.com/articles/d41586-019-03431-5

https://arxiv.org/abs/2006.00255

Thanks. I'm aware of what microscopic means. Which is clear from the next sentence in my comment that is only 3 sentences long.

Wow, how'd you figure that one out?

There's this thing called "the edit button". But what does it mean for life to "Still be microscopic"? Is a multicellular organism not a colony of differentiated microscopic clones?

Yes. See: all sentient life that exists on Earth evolved from microscopic life.

Reddit has an edit button. OP initially did not include "while still being microscopic".

What do you think "what if" means? If a quantum computer could navigate a hypersonic missile, then... a quantum computer could navigate a hypersonic missile.

If you think that quantum computers have some sort of advantage when it comes to communicating across vast distances or through interference, that's not how quantum computers work. I assume you think entanglement allows for communication. It doesn't.

Which is really ironic considering what a smug dipshit you are when replying to people as if they should be able to interpret your stupidly vague question with no detail that's based on a completely false premise.

You need to differentiate between independent variables and dependent variables. Your reasoning would be correct if our existence relied upon the existence of earlier civilizations, but it doesn't.

Imagine a bunch of civilizations that all formed independently, across a large span of time. If they all assumed that they evolved at the time in the age of the universe where a civilization is most likely to evolve, they would have a better chance of being correct than any other assumption.

This is why we should assume we are at the peak of the distribution.

You might find that your reasoning is more relevant when it comes to the doomsday paradox.

No it wasn't. They quoted the part they were questioning. Couldn't be much clearer.

How did you conclude that we "go in a straight line straight ahead"?

You are. What does that have to do with my question?

How did these ancient andromedans get here faster than the light emitted from them?

What's the alternative? That Earth remains habitable for humans forever? We know for a fact that won't happen. How could it not be "unsustainable"?

> It's important to note that the expanding space isn't really measurable on small scales yet, and won't be for MANY MANY years.

The rate of expansion of the universe isn't increasing. It will never increase the space between particles on small scales. That's not what is meant by "the expansion of the universe is accelerating".

Probably the most impressive pre-telescope discovery to me is axial precession. It is a 26,000 year long cycle. There are very few "events" to notice that would indicate something is even happening, and those things that you could notice are so gradual that even in an entire human lifetime, the change would be minuscule. With things like predicting eclipses, it's pretty obvious that you're going to notice an eclipse when it happens, and very quickly start to want to predict how they work.

WIth axial precession, there's the two possible states of "having a pole star" and "not having a pole star". People also noticed that stars that never dipped below the horizon in the past now would, and vice versa, or that stars that had never been visible at certain latitudes now were, and vice versa. But it's only a change of about 1 degree every 75 years. Truly impressive.

The actual answer is that the starting distances are nonzero, and with nonzero starting distances, you can get any size with the right rate of expansion. The "initial singularity" with infinitely small size is a mathematical anomaly, a result of naively running things back in time further than we know how to.

No rate of expansion, when multiplied by 0, gives you a positive distance. Something with infinite density cannot expand to something with finite density. The initial state of the universe as far as we are able to talk about it is hot, dense, and low-entropy, but it is not infinitely small.

So, any answer that involves some rate of expansion as the reason is incomplete, because without nonzero initial distances, you just get zero expansion.

Now, with all that out of the way, the answer to "how can the universe be 93 billion lightyears across if light has only had 13.7 billion years to travel" is just that the way we talk about the size of the observable universe is about how far apart those things would be from us now, at this moment in cosmic time (their comoving/proper distance). The majority of the observable universe is already unobservable, if by "unobervable" you mean "light emitted from it right now will never reach us". But we can see their past, and thus they're part of the "observable universe".

I didn't say that it doesn't expand. I asked why you feel that there has to be something for it to expand into for it to expand.

Expand is just the best word we have for what space does, it doesn't mean it has to be exactly like other sorts of expansion you can think of.

Space is expanding. Space is not expanding into anything. The distances between things are just getting bigger.

Why do you feel that space has to expand "into" something? "Into" requires some sort of spacial relationship. If there was something for space to "expand into" then that would just be space.

Yeah, notice how it's specifically phrased in a vague, meaningless way? "Headed our way" means nothing. It doesn't say that it's going to hit us.

>Is it really going to hit us

No, and outside of clickbait headlines, where have you seen someone actually say it is?

It's a potentially dangerous asteroid, but not on timescales that are relevant to your lifetime.

In general, asteroids coming from the direction of the sun that we have no way of detecting until they're just a few hours from hitting are a real worry though. But there's nothing you, personally, can do about that either other than choosing a career that helps solve it, so you shouldn't worry about those either.

This really doesn't solve anything. While there would be alien civilizations that didn't exist yet for you to see evidence of in the light you're receiving, there would also be alien civilizations that are now extinct that you would ONLY be able to see because you're receiving old light. Even if life is more abundant at this stage in the age of the universe, it still doesn't explain the total lack of clear evidence of aliens when we look at the universe.