I was watching a documentary about astronomy. In it, the narrator claimed that Jupiter can make the sun shift by as much as 500-thousand miles.
So that must mean, when Jupiter is in alignment with Earth, the sun is now 500-thousand miles closer to it. That seems like a lot! Certainly enough to cause significant change.
Am I missing something here?
[FTR: I believe what climatologists are saying about global warming. This thread is not intended as a “Gotcha” or anything silly like that. :))
Mostly because of the Inverse Square Law…
Let’s do a thought experiment with numbers that are based in reality, but not exquisitely accurate because, as you might see, the differences are almost irrelevant.
Assume the Earth is 92 million miles from the Sun (it is on average)
The Inverse Square Law governs how much radiation emitted from the sun impacts the Earth - a factor in this calculation will be 1/(distance[sup]2[/sup])… put in 92 million miles as the distance and the factor is 1.18 * 10[sup]-16[/sup]
Now assume Jupiter changes that distance to the sun by 500,000 miles. Put in 92.5 million miles, and the factor is 1.17 * 10[sup]-16[/sup]
The difference is very small compared to the total distance between the Earth and the Sun.
A couple other factors that may be less important that impact on your question are that Jupiter has been present for hundreds of thousands of years, and so its effects on the climate (as small as they are) already were factored in before humans started adding more greenhouse gases to the atmosphere. Another is that Jupiter and Earth will be aligned only during a small portion of the year, when they happen to line up on the same side (or opposite sides) of the sun, so its effects would be minimal during other parts of the year.
Possibly relevant:
Not just minimal, but opposite. Jupiter’s orbital period is about 12 years, so Earth completes an orbit while Jupiter hasn’t moved very far; this results in a cycle of “sun is closer than average” followed by “sun is farther than average” repeating with a period of just over a year. IOW, any effect due to Jupiter jerking the sun around it is cyclic and occurs on a timescale far shorter than climate change is happening.
What makes you think that Jupiter does not affect global warming?
According to this scientific paper, the effect caused by Earth’s alignment with Jupiter accounts for +/- 2.5 degrees C, but that effect is swamped by the much larger effect of Earth’s tilt which swings from about +20 to -10. Sometimes the two effects are in sync and add up; other times they’re out of sync and partially cancel each other out. But both of them are background noise when you’re trying to measure tiny increases in the global average over a span of decades.
You might as well ask the question “Why doesn’t wind affect the speed of runners doing laps around a track?”. The correct answer is that wind DOES affect their speed, causing them to slow down when running into a headwind and speed up running with a tail wind. But it’s hardly worth paying attention to if the race involves several laps around the track and you only care about the finish time, i.e. average speed. Yeah, if you measured the split times for each 100-meter section of the race you’d see slight increases and decreases due to which way the wind is blowing, but over the whole race it averages out.
So, yes, Jupiter affects the global average temperature of Earth at any one time but the effect will average out when you’re measuring across decades.
Good point - if Earth, the Sun, and Jupiter are aligned in April to have the Sun closer to Earth - they will be aligned again the next May or so with an opposite effect, the Sun further away from Earth.
The sun also isn’t constant. It tends to cycle between what we call the solar minimum and solar maximum on roughly an 11 year cycle (it varies, sometimes as short as 8 or 9 years and sometimes as long as 14 or so, the average is 11).
This solar cycle does affect the average global temperature, and has been linked to some changes in weather patterns.
As far as global warming goes, though, while the solar cycle does affect the Earth’s temperature, it’s just a periodic effect. The Earth will get slightly warmer and slightly cooler based on where the sun is in its cycle, but at the end of the cycle it will be back to where it started, temperature-wise.
Any effect Jupiter might have on the Earth’s temperature would be similarly cyclical, and would not contribute to global warming, which is a constant increase in global temperature that has been observed for centuries.
That or we can note that the earth at perihelion is 91.4 million miles from the Sun and 94.5 million miles at aphelion. A difference of 3.1 million miles which is a lot more than the 500,000 miles in the OP and it happens every year.
No, the inverse square law makes it worse. If the decrease were linear, you’d expect a difference of about 1%. But because the of the inverse square law, the difference is more than 2%.
Comparing 1.18E-16 to 1.17E-16 isn’t helpful. Let’s look at it this way. At 92 million miles, Earth intercepts 174 petawatts from the sun. At 92.5 million miles, it’s 172.1 petawatts. At 91.5 million miles, it’s 175.9 petawatts. That’s a difference of about 2.2%. Now consider the fact that Earth’s average temperature is about 288 Kelvin. Increase that by 2.2% and you’d have 294.36 Kelvin, which is an increase of more than 11 degrees Fahrenheit. That’s the difference between living in Pensacola Florida vs. Washington DC.
Increasing the rate of incoming flux to a radiating object does not increase its temperature linearly.
Global warming exists already, there’s no way that Jupiter can effect it.
For the record, the heat output of the sun (solar irradiation) is tracked by NASA (and, presumably, other space agencies) and is factored in to models of the climate.
The average global temperature does rise and fall with solar irradiation to a notable extent and the fact that solar irradiance was on the rise during (if I recall correctly) the 90s made it more difficult to determine whether global warming was human caused or not. But with more data, volcanic events, a reduction is solar irradiance, etc. the exact proportions are now (I believe) fairly well locked in.
One point that hasn’t been raised yet is that the Earth does not orbit around the Solar System barycenter. When Jupiter pulls the Sun around, the Earth mostly moves along with the Sun. So the distance won’t vary by nearly as much as folks are saying.
This is why we use 50 year time intervals for our climatic averages … comparing the past 50 years with the previous 50 years will “average out” the effects of Jupiter’s orbit, solar cycles, El Nino/La Nina cycles and whatever else that causes changes in only ten or twenty year cycles …
This was what I was going to point out. Part of the Milankovitch cycle is induced by Jupiter and Saturn.
But we are talking about effects over tens of thousands of years. Not anywhere close to explaining what’s been going on the last 50 years.
No known astronomical effect can explain recent changes. The time scale is either too long or it’s a too short term cycle. And ignoring the coincidental increase in CO2 is ridiculous.
It’s like letting someone off for murder since people die naturally all the time.
Thank you for this - I was just about to post something similar.
I’ve had a little more time to think. 500,000 miles is the amount that the Sun is deflected by Jupiter from the Sun’s ordinary path through the Galaxy (an observer on a distant star would see this deviation from the relatively straight path the Sun would normally take - if the distant star were properly oriented relative to the plane of the ecliptic) - it’s easy to see why, since Jupiter is about 500 million miles from the Sun and has about 1,000th the mass of the Sun. But in the first order, the Earth is pulled the same amount by Jupiter as the Sun is, so Jupiter causes no deviation of the distance from the Earth to the Sun to that order - we have to go to higher order effects to see Jupiter’s effect. I’d expect it to be a tidal effect, so I’d expect the magnitude of the effect of Jupiter on the Earth’s distance to the Sun to be proportional to 1 over (5 to the 3rd power) (or 1/125), since Jupiter is on average 5 times as far from Earth as the Sun is - so we’re looking at something like a 4,000 mile effect, not a 500,000 mile effect (all this is “back of the envelope” - it might be off by a factor of 3 either way).
I would like to retract that cite. Upon further examination, I am convinced that it’s not really a scientific paper, not based on scientific research, and not peer-reviewed. It looks like pseudo-science to me. Some of what it says is probably accurate, but I no longer trust it as a source.
However, I stand by my statement that fluctuations up and down over a period of months will be washed out when looking at a long-term trend over years and decades. Strictly speaking, the position of Jupiter might affect Earth’s Global Average Temperature, but Global Warming isn’t just about GAT, it’s about the upward trend of GAT measured on a time scale of years and decades. Imagine a business that makes more profit in the summer time and less profit in the winter time. If you are trying to determine whether the business is more profitable now that it was fifteen years ago, the summer-winter fluctuation would be irrelevant. It doesn’t even matter whether you plot the yearly averages or the monthly averages, as long as your x-axis includes an equal number of summers and winters.
cite? This seems counter-intuitive to me. According to this NASA web page, all the planets (including Earth) orbit around the solar system’s barycenter. Granted, this web page looks like it was written for a sixth grade text book, but I still would expect it to have accurate information.
Another thing to consider is that the normal difference between summer and winter distances from the sun is 3 million miles - 6 times larger than anything Jupiter does.
And… the Earth is closer during winter in the northern hemisphere, and farther away during summer, but the actual angle of incidence of the sunlight far outweighs that small amount of distance, making summer hotter because the light hits more directly, despite being 3 million miles further away.
I think that that page is seriously mistaken (or at least, poorly worded enough to be seriously misleading). It’s far to say that the Earth orbits the Earth-Sun barycenter - that’s a convenient reference frame to use for some purposes, but to say that it orbits the Sun-Jupiter barycenter is just wrong.