# Star distances

So I got it all up in my head that maybe the stars are closer than they appear. Like the scientists and astronomers could be wrong? I understand the light years but thats all angulation math. Could it be that they are closer?

How close do you think they are?

I’m thinkin maybe 200000 miles. something we could rocket to

it just seems they are so bright. like alpha centari. I get that light has to travel. but its gotta be pretty big

Well, the Moon is closer than that, so I would think that if there was a star that close, we would know it.

There’s not much in the way to dim the light.
You can see a match flame at 10 miles, if the night is dark enough.

Why do you think that?

you would think yes, but I’m sayin, maybe we’re wrong. I’m not thinkin’ of space travel or stuff like that. More of a physics question

The moon is 240,000 miles away - which is significantly farther than Neros’ star.

Neros - Are you by any chance, lying in your back yard with a fat roll-up looking up at the wonders of the night?

Duh.
Yeah, I even looked it up to double-check.
And still got the inequality wrong.

I think I got myself all wacked out on that book. By Arthur C. Clark. “The Light of other Days” Computers that created worm holes to galaxies and stars.

They can’t be that close without violating what we know about physics.

For example, we know some things are very redshifted. As long as the laws of physics work the same out to these stars, they’re traveling 200000 miles away from earth every hour. That’s actually a bit of an underestimate but illustrative, nonetheless.

That’s just one measurement. Not even a distance measurement, not that it has to be.

Everything we know about stars is consistent with the idea they are unimaginably far away from earth. Lots of the things we know are true about physics (because we can test them right here on earth) would come under question if they were somehow mystically right next to us.

No.

Any other questions?

Forget about the laws of physics - we’d be violating the laws of trigonometry. At one point you might argue that the distance to the sun is wrong, but since we’ve been to Venus we can be pretty confident that is right. (We can check the odometer on the probe.) The OP should look up parallax.

Wouldn’t a lot of astronomers (both professional and amateur) notice when all of those stars passed in front of the moon rather than behind it?

(Or for that matter when they passed in front of Jupiter rather than behind it?)

Of course. What you may want to know is what would have to be wrong for that to be the case? Which means you want to know how we know how far away the stars are. For stars within about 300 light-years (which is a lot of the stars you can see at night) we know via the method of parallax: we measure the position of the star in the sky today, and then again in 6 months, when the Earth has completed half an orbit around the Sun. The star will have appeared to shift very slightly against the background of much more distance stars. This is the parallax. It is the same thing that happens when you close one eye, then the other, and look at a nearby object – it will appear to shift positions, because your eyes are looking at it from different angles.

You can work out, via ordinary trigonometry, how far away the star is from the measured shift in its position, and knowing the diameter of the Earth’s orbit.

So for that to go wrong, we need the diameter of the Earth’s orbit to be rather badly wrong, which means the mass of the Earth or Sun isn’t what we think it is, or we’ve measured the length of the year wrong, plus all our calculations for how to send spacecraft to other planets is working out through some miracle because we actually have no idea where we are. Or another possibility is that the trigonometry is wrong, which could happen if space were much more strongly curved near the Earth than we think, in some odd way. One might wonder why it would be curved, since our present theories say that happens only in the presence of very large masses, and you’d think we’d notice something like that. But maybe the theories are wrong. I suppose it could also be some perverse motion of the star would give it a strangely small parallax – but not all of the nearby ones, that beggars the imagination.

The distance to stars farther away tends to be done with “standard candles,” like Cepheid variable stars or supernovae.

It’s possible in the same sense that it’s possible that the Universe came into existence last Thursday, with all of our memories of times before that created at the same time. That is, one could contrive extremely complicated models which would allow for it, but such models are literally insane.

It would violate direct observation with optics alone.

If they were that close—hell, if they were even just outside the boundary of our solar system—we’d be able to resolve a disc under magnification (perhaps even with the naked eye for some red giants). Alas, under the strongest magnification, they still only resolve as points. Because they’re so bright, and firikkin’ far away, in case you were wondering.

Does this mean that we have no way of measuring the distance of the farther background stars?