#distances

[mapsontheweb]

Vladivostok is closer to Darwin than to Moscow

[froggybangbang]

Have you ever seen a poster and thought.

Wait what.

I just did so i googled

Huh. That seems.... not that far? What about...

Okay. Okay that's... still.... but maybe I'm seeing distances wrong let's try what the poster said

.....

Huh. That's. I'm. Wait what is...

Okay so the international space station is roughly 10 times closer to me than the west coast is that's fine this is fine I'm fine what

[dodgerkedavra]

regula

for the @drarrymicrofic prompt rule

“Try,” Draco says, three hundred and seventy-eight days after the war. “Try once.”

His footsteps retreat. 

Harry stares at the ceiling.

A paper crane flutters overhead. Lands.

Not even a foot. Both beds, same wall.

“Is this long enough?” Harry whispers.

The other mattress creaks.

Draco’s footsteps come back.

[dreaminginthedeepsouth]

Caleb Hahne Quintana (Mexican-American, 1993) - A Flicker in the Ancient Rhythm (2025)

* * * *

“Children make you see distances. What do you mean “distances”? Lazer paused and picked an olive from the plate. He spun it slowly on the toothpick. Well for example this morning I was sitting at my desk at home looking out on the acacia trees that grow beside the balcony beautiful trees very tall and my daughter was there she likes to stand beside me and draw pictures while I write in my journal. It was very bright this morning unexpectedly clear like a summer day and I looked up and saw a shadow of a bird go flashing across the leaves of the acacia as if on a screen projected and it seemed to me that I was standing on a hill. I have labored up to the top of this hill, here I am it has taken about half my life to get here and on the other side the hill slopes down. Behind me somewhere if I turned around I could see my daughter beginning to climb hand over hand like a little gold animal in the morning sun. That is who we are. Creatures moving on a hill. At different distances, said Geryon.”

― Anne Carson, Autobiography of Red

[ticklingtimetickstotest]

[zespaceblog]

The Cosmic Distance Ladder, and Hubble/JWST

If you want to know how old the Universe is, you need to know how far away things are, and it may not be initially obvious just looking up in the sky how far away anything is.

Radar

For things inside our own Solar System, good old fashioned radar can tell you, by simply timing how quick a return of a EM wave takes. If you know the speed at which EM waves travel, then you have a distance.

Parallax

But for objects that are light years away, it's unlikely such a system would even hit the object you aimed at, never mind the length of time it would take to return.

This is where Parallax comes in, using the Earths passage around the Sun to have two different angles by which to view the object, and see how far it's moved against other objects, particularly those that are just too far away to be measured to move at all.

Main-Sequence Fitting

This too is great for all the closest stars, but as you move out further, it becomes impossible to measure, and then we fall back on measuring the distance to clusters of stars by comparing them with the known expectations on the HR diagram. The problem with this is, you're basing your observations on an average which may or may not be similar in the cluster you're looking at, so there's a 1-2% error margin, and you may have spotted this when something is given a +/- 50 light years on it's distance.

Cepheid's

Moving outside of the Milky Way, the error rate becomes too large for clusters to work, so instead a type of variable star known as a Cepheid is found in local galaxies, and observed through it's high/low cycle of variance. Cepheid stars all have exactly the same pulsation period, and so the luminosity of the star between pulses, gives away the distance.

Type 1A Supernova

Moving even further out beyond the ability to pinpoint actual stars, type 1A supernova can be used, although only when one happens. The brightness of such an event is always the same, so by measuring the apparent brightness, you get an idea of the actual distance.

So what's all this got to do with Hubble and JWST ?

Hubble Constant

Well, measurements of the more distant Cepheid and Supernova's used Hubble previously which was accurate enough to put the Universe at around 13.8 billion years old but it's calculations of the speed of expansion of the Universe (The Hubble constant), was still vastly different to the after-glow of the big bang and the figure it gives. Some suggested that Hubble may have had inbuilt errors that were throwing all the observation data off, so enter JWST, who made exactly the same calculations using IR instead of visible light, and came up with identical results to Hubble.

It doesn't resolve the Hubble tension, but it does validate the Hubble observations at the distances where Cepheid's and Supernova 1A could be used to calculate distance and expansion.

It's possible of course that the "Constant" wasn't constant, and that the early figure represents a true calculation of what was going on or that there is something else missing in the puzzle which we're not accounting for.

Either possibility is exciting, and for all those starting out in Astronomy, it just shows there's SO Much to learn, in fact, the more we learn, the more we realise how much more there is to learn ! A ladder in of itself.

[makewavesandwar]

What is the longest distance you would consider a ‘short’ hike/walk?

any distance hike/walk is long to me

1 mile (1.6 km)

2 miles (3.2 km)

3 miles (4.8 km)

4 miles (6.4 km)

5 miles (8 km)

6 miles (9.6 km)

a further distance would still be short to me (details in tags)

some other nuanced answer (details in tags)

Voting ended onJan 18, 2024

sorry to be miles-centric I am regrettably USAmerican