Why is sunlight warmer than light from bulbs?

64 views

I get that the sun is huge energy source, but it is so far, and the light from bulbs is just as bright as the sun

In: 0

Sunlight has stuff like UV in it that lightbulbs don’t have, also sunlight is still brighter than most lights anyway

Artificial light is not nearly as bright as the sun, your eyes are just better at adjusting to different light levels than you think they are.

Most lightbulbs are specifically designed for minimal heat output. No sense wasting energy on heat when the goal is to illuminate the room.

Light from lighbulbs isn’t even vaguely as bright as the sun.

The sun is very far away but it is very (very very very very very) powerful.

Solar flux (the amount of energy the sun puts out) is about 1300 W/m2.

So if you focus *all* the power of 13 100W light bulbs on 1 m2 then that’s roughly solar brightness. That’s enourmously more powerful than any normal light source. We use just a few 100W bulbs to illuminate an entire room (tens of m2).

Bright light looks bright, relative to the sun, because your eyes have a frankly ludicrous ability to operate well over a *huge* range of brightness.

The intensity of the sun’s light per unit area is much greater. It does not look that way because our eyes adapt over time. But turn on a lightbulb during a sunny day, and you’ll see how the illumination of the room changes very little, and the bulb itself looks quite weak and doesn’t blind you. The sun delivers around 1 kW per square meter during summer. A typical lightbulb or set of them in a room have the power of 0.1-0.2 kW for the whole room of 10 or so m². Some of the radiation is trapped by glass, but that is the same for sunlight going window glass.

It’s because of wavelength. Not all light carries enough energy to be absorbed by your skin.

In incandescent (old filament style) lights, you”ll find that not only will they warm your skin. They’ll burn it much easier than sunlight will.

This is because there is no filtering of light that takes place. They release both light and heat, or photons that have variable wavelengths producing some that have enough energy to be absorbed by your skin, heating it; While others do not have that same energy and create only light as they scatter off of it.

LEDs and modern lighting are tuned to *only* produce photons of the wavelengths of scattering.

>light from bulbs is just as bright as the sun

It isn’t though. Direct sunlight is a lot lot lot brighter than any bulb you can buy.

Sunlight is wayyyy brighter than the light from bulbs, your eyes just mask it

If something on a light meter measures 10x brighter you’re only going to perceive it as being about 3x brighter.

We measure brightness of a space in Lux where higher is brighter. A normal room might be lit to 100 lux while a bright office might be 500 lux. An overcast day is 1000 and a clear day is closer to 10,000 lux with direct sunlight being up to 100,000 lux.

So the reason sunlight is so much warmer than light from bulbs is because direct sunlight is about 1000x more intense than standard room lighting

The light from (most) lightbulbs isn’t nearly as bright as sunlight.

Think about all the times you’ve been outside and needed to put on sunglasses because the light was so bright you had to squint. Have you ever been in an indoor room where you needed sunglasses because the room was uncomfortably bright? The sun is so bright we can’t look directly at it without hurting ourselves.

Other have correctly said that light bulbs are less bright than the sun, but we usually use them in rooms that would be dark. If you take a light bulb outside on a sunny day, you will notice that it is not nearly as bright.

In addition, modern light bulbs (“plastic” LED and “coiled” CFL) are specifically created to avoid generating heat, because it wastes energy and makes the bulb burn out faster.

Old incandescent bulbs (metal coil inside a glass bulb) generate quite a bit of heat, and can be used to keep (small) plants or animals warm. E.g. turtle enclosures needs a “warming” light.