Recent comments in /f/space

SailingNaked t1_j680vmz wrote

That is where OP and you are wrong, and that's their point I wanted to clarify. The words are interchangeable. The Hubble flow has a speed and distance component... (km/s)/Mpc... speed over distance. Rate of expansion is just another expression of the speed of expansion that new space is created.

Edit: to try my hardest to clarify and settle this issue...

The expansion is given as (km/s)/Mpc.

That means that there is a rate over a distance.

If you take (10 km/s)/10 km or (20 km/s)/20 km... they are the same.

When the denominator is bigger the numerator will be bigger.

When the distance is greater the speed will be greater.

They are still the same...

(10 km/s)/10 km = (1 km/s)/1 km

(20 km/s)/20 km = (1 km/s)/1 km

The expansion rate/rate of expansion/speed of expansion are all the same everywhere.

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nicuramar t1_j680kt5 wrote

> I would say our best candidate for a planet with intelligent life. That’s cheating though since we don’t have one (maybe life, but no signs of intelligence yet).

I was gonna say “earth” until you added the last bit ;)

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nicuramar t1_j6807ie wrote

> At any point in space, the Hubble flow is the same. That is why it’s called a constant. It is the same everywhere.

Yeah, but you said “speed of expansion” in the other comment, which doesn’t exist, since it’s a rate ;). Maybe that’s what they meant.

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EasterBunnyArt t1_j67x6q0 wrote

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space-ModTeam t1_j67qm2a wrote

Hello u/SlickFire5555, your submission "Need Help With Sci-Fi" has been removed from r/space because:

  • Such questions should be asked in the "All space questions" thread stickied at the top of the sub.

Please read the rules in the sidebar and check r/space for duplicate submissions before posting. If you have any questions about this removal please message the r/space moderators. Thank you.

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SailingNaked t1_j67mdr0 wrote

At any point in space, the Hubble flow is the same. That is why it's called a constant. It is the same everywhere.

The observation that farther things move away faster is just that - an observation. They aren't so much moving as they are just getting more distant. Every point between the observed object and the observer is expanding at the same rate. It's not expanding faster the farther away the object is... it is just observed to be faster because there is more space expanding in between.

The speed of expansion is the same. Just when you have more space expanding, you move apart faster.

Edit: Maybe I can make the point clearer...

The rate of expansion is the same everywhere.

The observation that the expansion rate is faster the more distant the observed object is just an observation.

The reason we observe it to be faster is because to our eye we see it moving away faster than something close.

The speed of expansion isn't faster for a distant object or a close object.

The more space (distance) there is between an object, the more space there is to expand.

That space expands at the same rate (Hubble flow).

The expansion isn't faster... only the amount of distance increases.

That distance increases proportionally (at the same rate) to the distance between observed and observer.

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Anonymous-USA t1_j67lqdf wrote

The speed of expansion isn’t the same everywhere, it’s 73 kps per megaparsec. The further the distance the faster the expansion (and redshift). And yes, as we both said, that Mpc distance is relative to the observer. And the aforementioned expansion rate is the same for all observers anywhere.

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SailingNaked t1_j67kxbj wrote

You are correct in a way. There is a visible distance limit that we can observe. This is because any light produced beyond that distance will never reach us... ever. Even traveling at the speed of light, the space between the source and the observer expands into a greater distance than the light can travel. It'll constantly head towards us, but it will never reach us. A little photon, lost in the ever expanding emptiness, continuing on to never be observed.

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Druggedhippo t1_j67kt1u wrote

There is no credible evidence for a total geomagnetic pole reversal during Roman times. The last one was at least 780,000 years ago.

There is however research that talks about localized evolution in the geomagnetic field, for example this one in Iberia

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