Posted by bikenaga 11 hours ago
https://commons.wikimedia.org/wiki/File:ESA%E2%80%99s_Mars_a...
If it was 100 AUs at closest approach, we would never have seen it. (https://en.wikipedia.org/wiki/Oort_cloud is still theoretical, even)
The chances of yesterday's Powerball numbers being 04 24 49 60 65 01 was about 1:300M.
You're doing the thing. https://commons.wikimedia.org/wiki/File:Survivorship-bias.sv...
It's close because we saw it. We saw it because it's close.
https://www.esa.int/Science_Exploration/Space_Science/ESA_s_...
This thing traveled light years to get here. Possibly over billions of years. 30 million kilometers from Mars and 300 million and 3 billion kilometers from Mars would all be close approaches. Any approach can be claimed to be close; that's the magic trick at play here.
I don't think you're responding to my claim, which is that the close passes to Mars and Jupiter seem very unlikely. Of all random trajectories through the solar system at the distance of this body, what fraction of them pass equally close to major planets? I'd even be willing to limit it to trajectories close to the ecliptic plane, because we may be scanning that plane more.
4.5AUs is as close as 0.2AUs from an interstellar standpoint. Both are equally likely, just as every Powerball number is equally likely. Any object of this nature we can spot is going to be quite close with our current detection technology.
Again, your argument is effectively like arguing that 04 24 49 60 65 01 cannot possibly be yesterday's winning Powerball numbers, because it's a 1:300M chance. The game must be rigged!
Now, if the next couple interstellar objects we detect also do a similarly close pass on Jupiter and Mars, there'll be something worth wondering about.
(Similarly, if tomorrow's Powerball numbers are 04 24 49 60 65 02, I'll have questions!)
It is/isn't the Singularity while we are going and not going into WW III, while Rama is maybe zooming by, while Modern Rome does the whole fall of the Republic nonsense, or maybe doesn't! While the H5N1 thing is still churning away reassorting in pigs!
Narrative superposition is exhausting.
One small thing we can all calm down about. =)
But also sometimes monitoring the world is useful. I'm very glad I was paying attention in February 2020, for instance!
I don't understand. How did you write this comment?
> I'm a totally blind software developer.
Welcome! I certainly hope this universe is better than your original one
Seeing how everything is going, though, I strongly feel like we peaked as a species and that, while we'll continue up for a (short) while, the downgrade is just inevitable.
I agree with you, but I have been experimenting with image processing using the data available from this satellite (as a hobbyist). Honestly, while it's impressive that we gather data from a piece of technology that's floating in space, the resolution of this is nothing to write home about. If I take anything away from my brief amount of experience with this, it's that we still have a long way to go in terms of the quality of our imaging of our surrounding space.
I haven't fully finished my processing yet and still need to tune the wavelength and account for some drift, but this is basically the state-of-the-art: https://tcdent-pub.s3.us-west-2.amazonaws.com/3i_atlas_10302...
https://www.ign.com/articles/physicist-brian-cox-thanks-yout...
to us, the sun appears to be the size of, let's say, a quarter held at arm's length. this is at 93M miles (1AU, or ~8 light minutes) distance. if we moved the sun 100 miles away from earth, it would take up the entire sky. now in the other direction, if we doubled the distance, to 2AU, it would appear to us as half its normal size and 1/4 as bright (irradiance follows inverse square law). at 3AU the sun would be 1/9 as bright and 3x smaller than a quarter. at 100AU, we're talking about brightness of 1/100^2 (one ten-thousandth) the sun's apparent brightness. with me so far?
Sirius A: the brightest star we can see; 25x more luminous than the sun; 2x the size of the sun; 8.6 light YEARS distance (544,000AU) from earth.
if we moved the sun to the same distance as Sirius A, it would appear 296 BILLION times dimmer and 544,000 times smaller. yet Sirius A is easily visible - the brightest star in our sky - despite being only 25x more luminous and 2x larger.
do you see the discrepancy? 25x more luminous doesn't compensate for a 296-billion-fold brightness loss. The numbers we are given don't make sense, not even close. (and this is without considering diffusion, which would make the discrepancy even worse.) i'm not proposing an explanation or a modification to the model, i just think the data don't make sense.
In the case of your thought experiment, the critical factor is that our eyes are able to observe and adjust to a very wide range of brightness in different conditions. Sirius A really is billions of times dimmer than the sun to our eyes (hard to find a good reference for that, but this mentions it: https://ecampus.matc.edu/mihalj/astronomy/test5/stellar_magn...).
Here, the math doesn't check out. That's my point.
I'm not saying "it seems like stars should be invisible but they're not", Im showing that inverse square law - which we can verify at human scales - predicts invisibility at stellar distances, and the proposed compensation (25x more luminosity) is insufficient by orders of magnitude.
Sirius is "billions of times dimmer" than the sun to our eyes IF you mean the Sun as seen from Earth versus Sirius as seen from Earth. But that's not the comparison. The comparison is:
Sun moved to 544,000 AU (Sirius's distance): 296 billion times dimmer than Sun at 1 AU Sirius at 544,000 AU: 25x brighter than that
25x doesn't bridge a 296-billion-fold gap, plus the eye's dynamic range is irrelevant; we're comparing what brightness should reach the eye versus what compensation the model claims.
If your claim is "the eye can see across many orders of magnitude, so even though the Sun would be invisible at stellar distances, Sirius being slightly brighter makes it visible," then do the actual calculation. Show that 25x more luminosity produces enough photons to cross the detection threshold. Because the math I'm showing says it doesn't.
You're assuming the model works and looking for why my intuition is wrong. I'm showing the model's numbers are internally inconsistent. Those aren't the same thing.
>I've found that when I have a thought that seems to contradict the "established" model of the world, I tend to just be missing some critical factor.
Does it bother you that to make relativity work, they had to invent dark matter and dark energy - 96% of the universe's mass-energy - as fudge factors? At what point does "missing a critical factor" become "the model requires constant patching to match observations"?
This would be a lot more compelling from someone who doesn't believe in astrology.
https://news.ycombinator.com/item?id=45631792
(It's interesting that you forget the inverse square law in that case.)
Here are the numbers as far as I understand them.
Apparent magnitude of the sun: -26.74 Apparent magnitude of Sirius A: -1.46
Excepted magnitude of the sun after moving to 544,000 AU: 296 billion times weaker, leading to +1.96 magnitude, according to a calculator (https://www.1728.org/magntude.htm).
I don't trust that calculator a lot, so to check that math, I used a formula to calculate the difference between those magnitudes (https://lco.global/spacebook/distance/comparing-magnitudes-d...) and got a result of 23.34. Not far off from the expected 25x difference.
So the sun at 544,000 AU wouldn't make the top 25 brightest stars in the night sky, but it wouldn't be far from that (https://www.britannica.com/science/list-of-brightest-stars-2...) and definitely well within what would be visible (https://en.wikipedia.org/wiki/Limiting_magnitude).
These are all numbers you just provided, with no source for them.
But even using your numbers, 300 billion is 3x10^11. The Sun provides about 10^5 lux, while starlight overall provides about 10^-4 lux[1], which is a difference of 10^9, meaning the difference between "all the starlight on a dark night" and "just the starlight from Sirius" would be around 10^2, which... seems about right?
1. https://en.wikipedia.org/wiki/Orders_of_magnitude_%28illumin...
We can spot a single photon in the right conditions. https://www.nature.com/articles/ncomms12172
And it's entirely washed out during the day. The full Moon is very bright, but it's still 400,000 times dimmer than the Sun when seen from Earth, and that's only ten different. The brightest star in our sky is simply not very bright; our eyes are just pretty awesome.
That star you are seeing is 25 orders of magnitude dimmer.
https://astro.wku.edu/labs/m100/mags.html
"While you may perceive one star to be only a few times brighter than another, the intensity of the two stars may differ by orders of magnitude. (Light intensity is defined as the amount of light energy striking each square cm of surface per second.) The eye is a logarithmic detector. While the eye is perceiving linear steps in brightness, the light intensity is changing by multiplicative factors. This is fortunate; if the eye responded linearly instead of logarithmically to light intensity, you would be able to distinguish objects in bright sunlight, but would be nearly blind in the shade! If logarithms are a faint memory, you should peruse a refresher on logs and logarithmic scales before continuing."
https://physics.stackexchange.com/questions/329971/how-many-... says looking up at a sunny sky lets you take in 3×10^14 photons per second per eye. Yet you can see a single photon! https://www.nature.com/articles/ncomms12172
Or, we can conclude the entire field in dozens of countries simply can't do math. Your choice.
You're comparing the Sun's illuminance at Earth (10^5 lux at 1 AU) to all starlight combined (10^-4 lux), then trying to work backward to what a single star should provide. That's not how this works.
The question isn't "what's the ratio between sunlight and all starlight." The question is: what happens when you move the Sun to stellar distances using inverse square law?
At 1 AU: ~10^5 lux
At 544,000 AU: 10^5 / (544,000)^2 = 10^5 / 3×10^11 ≈ 3×10^-7 lux
That's the Sun at Sirius's distance. Multiply by 25 for Sirius's actual luminosity: ~7.5×10^-6 lux.
Your own Wikipedia source says the faintest stars visible to naked eye are around 10^-5 to 10^-4 lux. So we're borderline at best, and that's with the 25× boost.
But moreover, you said "the difference between all starlight and just Sirius would be around 10^2." There are ~5,000-9,000 stars visible to the naked eye. If Sirius provides 1/100th of all visible starlight, and there are thousands of other stars, the math doesn't work. You can't have one star be 1% of the total while thousands of others make up the rest - unless most stars are providing almost nothing, which contradicts the "slightly brighter" compensation model.
Address the core issue: inverse square law predicts invisibility. The 25× luminosity factor is insufficient compensation. Citing aggregate starlight illuminance doesn't resolve this.
The Sun's (or any star's) emitted energy is measured in terms of solar luminosity.[1] The nominal value of solar luminosity is 3.83×10^26 watts. At twenty five times as luminous, Sirus' luminosity is 9.5710^27 watts. We can divide that by your 296 billon times, which gives.. 3.2x10^16 watts as what actually makes it to Earth. If the we convert that back into solar luminosity (to figure out the apparent brightness at Earth), its 8.3595 10^-11.
Now, if we look up at the sky, and check how bright the Sun and Sirius are from Earth on the magnitude scale, which each step is ~2.5 times brighter than the one below it (and vice versa), the Sun has an apparent magnitude of -27, while Sirus' is -1.46. I.e. the Sun in the sky is about 8 billion times brighter that Sirus is. That's within an order of magnitude of what its calculated solar luminosity should be. Again, it seems about right.
"Does it employ a power source that is hotter than the Sun?"
Sigh.
What most stand out is the sheer amount of closed mind people in the accademia, Avi is not afraid of making suggestions of what it might be and even saying “if it turns out of being a rock, so be it”.
> even saying “if it turns out of being a rock, so be it”
I don't doubt it! He'll get another chance the next time we spot another one.
Does everyone at any prestigious institution have some duty to remain conventionally mundane in all their musings?
Is there any reason to think such hypotheticals are, on net, more harmful than helpful?
Isn't tenure (like Loeb's) designed to encourage a fearlessness around topics & speech?
He'll have the same to say about the next one.
1. https://en.wikipedia.org/wiki/1I/%CA%BBOumuamua
2. https://en.wikipedia.org/wiki/2I/Borisov
3. https://en.wikipedia.org/wiki/3I/ATLAS
2/3 of them Loeb has made wild claims about.
I miss the days when tabloid fodder stayed in the tabloids.
Even with cryovolcanoes, the power source is not on the comet; it's the sun.
