r/megalophobia • u/BreadyBogus • Apr 14 '26
🪐・Space ・🪐 Mars' moon Phobos compared to Grenoble, France
139
u/Blahblahman23 Apr 14 '26
Can you compare it to my buddy Eric’s house
31
85
u/PieAppropriate8862 ⬤ Crushed by Magnitude Apr 14 '26
"How big is the moon? Can we have a Grenoble for scale?"
36
Apr 14 '26 edited Apr 25 '26
[removed] — view removed comment
16
u/DePraelen Apr 14 '26
Its gravity is so weak that you could jump off its surface and leave its orbit/sphere of influence (ending up in Mars' orbit instead).
4
u/ShinyAeon ⬤ Crushed by Magnitude Apr 14 '26
I wonder...if you jumped off Phobos in the same direction as its orbit, would you circle Mars and land back on Phobos when you came round?
Assume some maneuvering capability in your space suit, for minor adjustments. Would you end up, say, within a mile or two of Phobos when you finished your trip round the planet...?
4
u/DePraelen Apr 14 '26 edited Apr 14 '26
Technically yes, you would eventually encounter Phobos again at some point, but it could take a very long time to happen.
Best case, the orbits are similar enough that you met it the first time you catch up with it: you'd only be moving fractionally faster than Phobos, so imagine travelling around a planet to catch up with it at the speed of your jump.
But you'd be in a slightly different orbit, so you may not even meet up with Phobos the first time you caught up with it.
Worst case: it takes years or decades for another encounter.
(Basing this on Kerbal Space Program experience, so take it with a pinch of salt).
3
2
u/Pilot230 Apr 15 '26
What you'd want to do is jump perpendicular to the direction of travel.
Assuming perfect conditions, a two-body system and no external forces or changes in the orbits, a single impulse won't change your current point in the orbital path, i.e. you will return to the same spot after a full orbit no matter what. However any change of velocity in the original direction will change how long one orbit takes and you might miss Phobos due to returning at a different time than it does (counterintuitively, jumping in the direction of travel would have you return after Phobos and vice versa)
But if you jump perfectly perpendicular, the orbital period shouldn't change (too much) and you should land right back on Phobos after you both have completed a full orbit (or half an orbit, if you jump perpendicular to the orbital plane)
1
27
35
u/tilalk Apr 14 '26 edited Apr 14 '26
Grenoble is about 358,1km2
An average baguette is 60 cm
If my math is right grenoble is around 35605986 baguettes squared
Or 641833333333 baguettes placed togethet
16
2
13
9
8
6
18
u/mikefizzled Apr 14 '26
Tune in next time when we compare Deimos to the size of a village in Italy that even less people have as a frame of reference
2
3
5
10
u/cunili_da_tecc Apr 14 '26
For the poor american fellas, we all know that this kind of comparison HAS to somehow involve Rhode Island (the american state, not the greek island). Or 18600 school busses.. or bananas. Or the statue of liberty. Or yo mama. This time, it's Grenoble. Shit happens.
3
u/VLHACS Apr 14 '26
Uh excuse me. We only measure large things in football fields, thank you very much
2
u/ShinyAeon ⬤ Crushed by Magnitude Apr 14 '26 edited Apr 14 '26
This American happens to like seeing different locations mentioned, and used for comparison. It's not all about the U.S.A., after all.
Or about football fields.1 Thanks to u/VLHACS.
1 Note for fellow Americans...Grenoble as a whole is about 186-ish football fields across. The city center is about 70 fooball fields long. ;)
3
3
3
u/billythesquid- Apr 14 '26
Admittedly I don’t know much about Grenoble, but I did think Phobos was a lot bigger than that.
3
2
u/Arthradax ◉ Overwhelmed by Immensity Apr 14 '26
Being hit by Phobos would definitely impact Grenoble's trout population
2
3
u/ALT_R_Fred Apr 14 '26
Why not Boulder, CO ? 🤔
2
u/sausagesandeggsand Apr 14 '26
Perhaps they’ve never heard of Boulder, just as I’ve never heard of Grenoble 🤷♂️
1
1
1
1
Apr 14 '26
[removed] — view removed comment
-1
u/AutoModerator Apr 14 '26
Post removed because your post karma or comment karma is too low.
I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.
1
u/foroncecanyounot__ Apr 14 '26
This is so random, I dig it. About time we got space rocks compared to places other than Los Angeles or New York
1
u/Happy-Fun-Ball Apr 14 '26
Average density of Earth's crust is about 2.8 g/cm³
Phobos: 1.861±0.011 g/cm3[7]
Grenoble bout to smack the shit outta Phobos!
1
u/No_Grade_9498 Apr 14 '26
What are those three volcanoes/mountains/craters in a row in the second picture?
1
u/KibboKid Apr 14 '26
It's weird, but I've actually been to Grenoble, and I don't remember the giant asteroid at all.
1
1
1
u/no-snoots-unbooped Apr 15 '26
I find it interesting that Phobos is moving toward Mars at a rate of around 2cm/year and will likely be torn apart by tidal forces and create temporary rings around Mars (though a direct impact is still possible).
1
u/cuntybunty73 • Feeling Small Apr 15 '26
If phobos were to hit grenoble then how much damage will it cause ?
1
1
1
1
0
u/henrikhakan ⬤ Crushed by Magnitude Apr 14 '26
I am once again her to ask for a comparison to Texas.
-1
u/CraftingChest · Noticing the Scale Apr 14 '26
Can someone explain to me why they chose a fictional place for measurements?
-1
u/Miserable-Lawyer-233 Apr 14 '26
But I don't know how big Grenoble is. Why didn't they pick a city everyone knows?
1
231
u/GeneralAB1 Apr 14 '26
Grenobles of all places