Searching for city lights on other planets

[Eldorado]

About a decade ago, I attended a conference inaugurating the campus of New York University in Abu Dhabi along with a colleague from Princeton University, Ed Turner. The conference included a tour through the neighborhood, during which the local guide bragged that their city lights can be seen all the way from the moon. Ed and I looked at each other and wondered: from how far away could the Hubble Space Telescope (HST) detect city lights?

During the following day, we calculated that the Hubble Deep Field could notice a city like Tokyo on objects in the Kuiper belt at 30–50 times the Earth-sun separation. But can we distinguish artificial lights from natural reflection of sunlight if they have a similar color?

https://www.scientificamerican.com/article/searching-for-city-lights-on-other-planets/

[acute]

Why is it..... We can't imagine a form of intelligent life that doesn't use similar senses to our own.

Maybe sight is a rare asset in the universe, and if you don't need sight, you don't need light!

[L.A.T.1961]

2 hours ago, acute said:

Why is it..... We can't imagine a form of intelligent life that doesn't use similar senses to our own.

Maybe sight is a rare asset in the universe, and if you don't need sight, you don't need light!

Bats can move around quite safely in the dark. 

But Its hard to imagine an intelligent race evolving without some type of method to detect their surroundings ?

Kuiper belt objects, when observed, are not competing with light from our star, other planets around distant stars would have any artificial light obscured by their own sun when viewed from Earth. 

[acute]

11 minutes ago, L.A.T.1961 said:

But Its hard to imagine an intelligent race evolving without some type of method to detect their surroundings ?

That's why I said "if you don't need sight", because you have another way of mapping your surroundings.

Our hearing evolved from feeling vibrations on the jaw. There must be countless alternatives to our 5 senses out there.

[TigerBright19]

Would be very difficult to focus on a distant planet during its night time cycle.  It's probably very difficult just to see them as they are with their Sun shining on them at day.  Can a telescope focus on a dark patch of space without the assistance of that alien planet's Sun for illumination?

 

 

[Tatetopa]

53 minutes ago, acute said:

That's why I said "if you don't need sight", because you have another way of mapping your surroundings.

Our hearing evolved from feeling vibrations on the jaw. There must be countless alternatives to our 5 senses out there.

Our 5 senses evolved to detect signals present in our environment.

Electromagnetic radiation that carries possible information about our surroundings. Sight.

Compression waves in liquid or gas surrounding an organism for possibly  useful. information. Hearing.

Various molecules suspended in liquid or gas that reveal information about emitters  of those molecules  in the environment. Smell and Taste.

Surface characteristics of nearby objects. Touch.

And some detection of gravity and positioning.  Balance.

Some earth organisms seem to be able to detect magnetic fields.

All of those senses are useful  because they detect signals present in the environment that can be  used to increase chances of survival.   There might be a lot of different methods that organisms evolve to detect  signals, but the nature of signals is largely determined by physics and chemistry.   If those signals are present, there is a good probability that interpreting them is useful for survival.  If EM radiation is available, isn't it likely that some detection mechanism will evolve to make use of it?

 

 

 

[acute]

1 hour ago, Tatetopa said:

Some earth organisms seem to be able to detect magnetic fields.

Everything with mass bends spacetime. Maybe that can be detected accurately.

 

Edited June 13, 2021 by acute
Gramma.

[Inn Spectre]

The existence of city lights indicate a civilisation coming to an inevitable end, so by the time we see them, they're gone.

[Rlyeh]

17 hours ago, acute said:

Why is it..... We can't imagine a form of intelligent life that doesn't use similar senses to our own.

Maybe sight is a rare asset in the universe, and if you don't need sight, you don't need light!

Light is abundant.

['Walt' E. Kurtz]

19 hours ago, acute said:

Why is it..... We can't imagine a form of intelligent life that doesn't use similar senses to our own.

Maybe sight is a rare asset in the universe, and if you don't need sight, you don't need light!

Exactly the orgin of the alien life form does not have to be simular to our scientific hypotesis.

the study of abiogenesis seems interesting since it aims to determine how pre-life chemical reactions created life under conditions different from earth. 

[Waspie_Dwarf]

On 6/13/2021 at 6:27 PM, acute said:

Why is it..... We can't imagine a form of intelligent life that doesn't use similar senses to our own.

Maybe sight is a rare asset in the universe, and if you don't need sight, you don't need light!

Who said we can't imagine a form of intelligent life that doesn't use the same senses as us?

You are putting the cart before the horse here and totally missing the point.

 

There are limits in what signs of intelligent life we can look for, as Arthur C. Clarke said,

Quote

Any sufficiently advanced technology is indistinguishable from magic.

How do we look for "magic" when we probably won't even recognise it. The sample answer is that we can't. So we are limited to searching for technological signs that we will recognise.

There are also the limits enforced on us by the laws of nature. @L.A.T.1961 mentioned echo location. That's a possibility BUT since sound waves can't travel through the vacuum of space then we can't detect them. There is no point looking for signs you can't detect.

We are limited to looking for signs we can detect and can understand. Illuminated cities ARE one of those signs.

[Waspie_Dwarf]

21 hours ago, acute said:

Everything with mass bends spacetime. Maybe that can be detected accurately.

 

And how will that help in the search for life? Short answer: it won't.

Living things are not an addition to a planet's mass, they are part of it. The mass of the Earth is exactly the same as it was before life. If all life were to go extinct tomorrow the mass of the Earth would not change an iota. We come from the Earth, we return to the Earth, in between we are part of the Earth. That will be true of any life on any planet.