Are Other Galaxies As Far Away As We Think They Are?

originally posted by: eManym
If a photon could perceive reality, wouldn't the photon's reality be one dimensional?

We can't really answer this question-- when you go to write down the equations that describe how time & length appear to a person travelling at the speed of light, you end up dividing by zero. We say that there is no well-defined reference frame travelling at c.

originally posted by: stumason
a reply to: Soylent Green Is People
How does this happen? Where does this mass come from?

I've never been a fan of saying that mass increases with velocity. As you approach the speed of light, however, it takes more and more energy to accelerate the same amount. Classically, since A = F/M, it looks like the same force provides less acceleration, e.g. an increasing mass. However, mixing classical and relativistic physics like that is kinda gross and not really accurate.

However, you can also consider that mass is energy. An object at a higher speed has a greater kinetic energy, and when you reach relativistic speeds, the amount of kinetic energy you have can be of the same order of magnitude as your mass-energy. So your overall energy (which is like your overall mass) has increased simply because you're moving. Your rest mass never changed.

a reply to: wirehead

Thankyou - this is what I thought but I always see comments such as "your mass increases" with no real explanation - that makes sense.

originally posted by: Bone75
According to commonly accepted science, if I were to take off from where I'm standing at the speed of light, and head towards the Andromeda galaxy, it would take me 2.5 million years to get there.

Yet according to time dilation, the faster you go, the more time slows down. So even though it appears to everyone else that it took me 2.5 million years to get there, I would actually be much less than 2.5 million years old.

How does science reconcile this paradox? How can they say definitively that it takes light from the Andromeda galaxy 2.5 million years to get here? Wouldn't that light be much younger than we perceive it to be?

No paradox. It just depends where the observer is.. ie, relativity.

If you were the photon, you'd arrive instantly.
If you were on Earth, it would take ~2.5m years

originally posted by: stosh64
a reply to: Bone75

IMHO, there is MUCH guess work when it comes to distances in space over 400 LY. And a lot of room for error in things within the 400 LY range.

They say that triangulation is the best method for stars within this distance, but the minute angles, even taken 6 months apart, and about 186 million miles apart, are so small I feel even these are guesstimates.

The first technique uses triangulation (a.k.a. parallax). The Earth's orbit around the sun has a diameter of about 186 million miles (300 million kilometers). By looking at a star one day and then looking at it again 6 months later, an astronomer can see a difference in the viewing angle for the star. With a little trigonometry, the different angles yield a distance. This technique works for stars within about 400 light years of earth.

SOURCE

For farther than 400LY they use brightness measurements, which makes me chuckle when I see statements like 250 million LY, or a billion LY. They really don't know.

As far as relativity and time, well, I will go wipe the drool from my chin and leave that to others to speculate.

It might make you chuckle, but you're not an expert, the scientists are. There is no 'speculation' on relativity, it's been demonstrated many many times.