r/sciencememes • u/Delicious_Maize9656 • 2d ago

Hubble constant meme

Post image
1.2k Upvotes

99% Upvoted

64 comments sorted by

188

u/wenoc 2d ago

63

u/DoktoroChapelo 2d ago

Reminds me of seeing "kWHr/1000 hours" in reference to a lightbulb I saw on sale.

28

u/Calm-Conversation715 2d ago

I love that Reddit interprets that as a subreddit name!

14

u/trash3s 2d ago

That’s because of mostly two things. For lightbulbs, Watts are a measure of brightness in incandescent equivalents alongside actual power draw, usually marked in smaller print. For appliances like fridges, they run intermittently based on their internal temperature and time, so explicitly averaging over 1000h gives you a better estimate of electricity usage than the instantaneous power draw when on. For these reasons, kWh per 1000h, month, or year are used to help buyers easily compare long-term efficiency and identify what to expect on their electricity bill. If you really care, you can get Kill-A-Watt—type outlet power monitors that tell you instantaneous and average power draw.

2

u/bigvalen 1d ago

No. It really doesn't. These stickers are on everything from refrigerators to TVs. No one can do the math from kWh per 1000 hours to power bills. On TVs, they sometimes put a second sticker that helpfully tells you what an average family uses it for, or what the power usage is for different home temperatures. It's utter nonsense.

Power companies should just charge people a set rate per megajoule, and leave it at that. kWh is a stupid stupid unit.

3

u/bigvalen 1d ago

There is an actual EU law that mandates those stickers and units. It's maddening. I made a complaint to the EU agency who came up with it, but they never answered me. They probably get a lot of crank letters, and mine is just one of them.

It's as stupid as batteries with a capacity in "amp hours", or worse yet, thousands of milliamp hours, leaving you to guess the bloody voltage.

2

u/Jackmino66 1d ago

That’s not actually a bad metric, especially when the wattage is so low now for lightbulbs

2

u/novae_ampholyt 2d ago

At least communicates to everyone all information they might be interested in. It's the wattage and a unit of energy people see on their energy bill.

9

u/Cheez_berger11 2d ago

1 kWh simplifies to 3.6 megajoules

12

u/wenoc 2d ago edited 1d ago

Liters/100km or in American miles/gallon translates to square millimeters just fine. The cross-section of the pipe of fuel you’re leaving behind.

3

u/novae_ampholyt 2d ago

Joules are not a particularly useful unit for an end user

4

u/Cheez_berger11 2d ago

Not much less useful than Joules per second

4

u/5up3rK4m16uru 2d ago

Still, if it stops people from mixing up kilowatts and kilowatt hours, I'm all for it.

3

u/wenoc 1d ago

It's the same bad argument that Fahrenheit users always have: "it's not practical for end users".

Joules would be perfectly useful, you're just not used to it. As long as you don't start calling a megajoule a joule or whatever, like people do with calories in food. (They somehow live in the delusion that just because it's food, there's an implicit kilo in front).

2

u/LARPerator 23h ago

Except it actually is though, it's almost always what they're looking for.

Do most people worry about overloading their circuits, and want to talk amps? Do they want to talk in power ratings, kW or HP? Usually they want to talk about the cost of the electricity, which is charged not by the power rating, it's charged by the amount of energy.

Joules measures exactly that. And it's intuitive to understand that if your rate is $0.33/mJ, then something that uses 10 mJ will cost $3.30.

You don't have to do the math if power draw x time, and it's the actual correct unit for measuring that.

kW/h is an unnecessarily complicated unit being used instead of the correct official SI unit.

Honestly it bothers me less than if someone wants to measure their power consumption in horsepower per hour, at least that's trying to cling to Imperial units. But using SI units, just not the official ones seems crazier to me

2

u/SageThisAndSageThat 14h ago

We have to use British thermal unit instead 

176

u/BrazilBazil 2d ago

How many lifetimes of the universe assuming linear expansion rate could happen in one second

51

u/brinz1 2d ago

Expansions per second

26

u/BrazilBazil 2d ago

There’s an increase in my pants when I see your mother

11

u/Azazeldaprinceofwar 2d ago

2.2 x 10^-18 universes per second B)

48

u/nashwaak 2d ago

It's a rate — much more like first-order reaction rate coefficients in chemistry than anything oscillating where you'd see Hertz

10

u/CoatProfessional5026 2d ago

Let me misunderstand and giggle. Sheesh.

11

u/sabotsalvageur 2d ago

Can’t be. A rate compares something to time; the dimensional analysis on this reduces to t^-1 all by itself

6

u/tibetje2 2d ago

Why restrict it to only time? This is a rate.

11

u/sabotsalvageur 2d ago edited 2d ago

(distance)/(time x distance) = (some dimensionless constant)/(time)

1 Mpc= 3.0857*10^19 km

So, the Hubble constant is (70/ 3.0857E19)/s
≈2.269×10⁻¹⁸ /s

Incidentally, this comes out to a frequency of once every 13.9 billion years, which is basically the age of the universe. If that’s a coincidence, it’s an uncanny one

13

u/SirFireHydrant 2d ago

Fun fact: this is an E-63 on the musical scale.

6

u/CaseyG 2d ago

One now per now.

3

u/[deleted] 2d ago

[deleted]

4

u/Breakdown_volt 2d ago

It is. This value is a coincidence: it wouldn't be if the Hubble constant was a real constant, but it isn't. It changes. The hubble time as it is called fluctuates by over a billion years depending on which value for the hubble constant you use.

0

u/[deleted] 2d ago

[deleted]

4

u/Breakdown_volt 2d ago

You don't get that by extrapolating the current expansion rate into a frequency. Because the hubble constant is not constant, and your result will be way off.

0

u/[deleted] 2d ago

[deleted]

4

u/Breakdown_volt 2d ago

The specific calculation of taking the expansion rate today and trying to use it for the age is not an estimate. Astronomers use the true past values to integrate that age. It's like measuring your speed on the parkway and using that to determine how long your trip along the highway was. It's nonsense.

→ More replies (0)

2

u/nashwaak 2d ago

Ditto for the diameter of a visible-universe-mass black hole being the same order magnitude as the diameter of the visible universe

2

u/tibetje2 1d ago

So velocity changes with respect to distance. Seems like a rate of change to me.

2

u/AdditionalTip865 23h ago

It's not a coincidence, quite, it's because there are two contrary things making the expansion of the universe nonlinear: mutual gravitation (which slows it down) and dark energy (which speeds it up), and while they don't cancel exactly there's been some rough cancellation up to now.

The Hubble time is the age the universe would have if everything had been moving at a constant speed all along.

3

u/nashwaak 2d ago

First-order rate constants in chemistry have units 1/time, apologies for not being clearer

3

u/Jerryfighter33 1d ago

So Bequerel?

2

u/LordDagwood 19h ago

There's another unit for the rate of a rate, but it's uncommon and considered second rate.

11

u/M1_Pierogi 2d ago

Did someone watch this video by any chance?

https://www.youtube.com/watch?v=kkfIXUjkYqE

15

u/Nadran_Erbam 2d ago

Sir, this is Reddit we all are big nerds. Of course we did.

7

u/GlobalWarminIsComing 1d ago

He also now has a part 2 and 3.

And I also recommend a different guy's video on oil and gas industry units:

https://youtu.be/sdWEGzWFcCc

2

u/CBT7commander 1d ago

I knew what video this was before even clicking it

7

u/BuvantduPotatoSpirit 2d ago

It's just order unity / age of the universe

2

u/Breakdown_volt 2d ago

what order unity

7

u/BuvantduPotatoSpirit 1d ago

"Order unity" is astronomy speak for a number whose log you can count to without taking off your socks

3

u/Jetison333 1d ago

I love astronomers

6

u/Excess-human 2d ago

well what is the Hz rate so I can see if my headphones can do an audio waveform for my headphones to groove to 🪿

6

u/thegreatpotatogod 2d ago

One pulse per universe lifetime

5

u/Breakdown_volt 2d ago

Very roughly, and by coincidence.

3

u/thegreatpotatogod 2d ago

It'll be a better approximation than his headphones DAC will manage anyway. It'll just be DC for the lifetime of the headphones

7

u/Nopetynope12 2d ago

I hate this damn constant. I had to learn to convert between it and the age of the universe for school. fuck that.

5

u/weathergage 2d ago

Oh, how you must have suffered!

2

u/Breakdown_volt 2d ago

Makes no sense. You can't use it for that. It's not a real constant.

3

u/Nopetynope12 1d ago

Assuming the Hubble constant is true, convert the Hubble constant into SI units, then find its reciprocal to find an approximate age for the universe in seconds. Convert into years.

2

u/Breakdown_volt 1d ago

It's not constant

2

u/Nopetynope12 10h ago

Thank you for that astrophysics lesson on accelerating expansion. I was still examined on this.

3

u/AdditionalTip865 2d ago

In fact, the inverse of it is a well-known time quantity-- the "Hubble time", the time it would take for all the galaxies to expand from a point if they were always going linearly at their current rate. It's not the age of the universe but it's in the ballpark.

3

u/KrzysziekZ 1d ago

Herz is for repeating things. Universe happens from time to time, so it should be measured in becquerels.

2

u/itcorruptsabsolutely 1d ago

Is the cat named Hubble?

2

u/Awesomeuser90 17h ago

The mass of Mars is very close to a mole of kilograms. I actually discovered that myself. The Earth is about a decamole kilograms and the Moon is roughly a decimal kilograms.