How old is the sunlight we see today?
170 000 years
Can we see in the past?
We are seeing into the past too. While sound travels about a kilometre every three seconds, light travels 300,000 kilometres every second. When we see a flash of lighting three kilometres away, we are seeing something that happened a hundredth of a millisecond ago. That’s not exactly the distant past.
How old is the light hitting Earth?
between 100,000 years and 50 million years
How old is a photon?
Now, by studying ancient light radiated shortly after the big bang, a physicist has calculated the minimum lifetime of photons, showing that they must live for at least one billion billion years, if not forever.
What is the real color of the moon?
gray
What color is the hottest flame?
blue
What burns hotter coal or wood?
Coal ignites at a temperature more than 100 degrees higher than wood, and it requires a hot bed of wood coals to get it started.
At what temperature does coal ignite?
around 300°C
Why do coal piles catch fire?
Spontaneous combustion: Coal has a tendency to self-heat due to the auto-oxidation of its compounds, making spontaneous combustion the most common cause of uncontrolled burning. There are thousands of uncontrolled coal fires across the earth, some of which have been burning for thousands of years.
How does a matchstick catch fire?
Stored inside the match head is another chemical called “potassium chlorate”. When it gets hot, it releases a lot of extra oxygen and heat. This makes the match head burn quickly and strongly. When you put it all together – the heat, the fuel, and the oxygen – you get a flame!
What temperature does diesel ignite at?
To ignite, the fuel must have a low flash point, but in order to avoid preignition caused by residual heat in a hot combustion chamber, the fuel must have a high autoignition temperature. Diesel fuel flash points vary between 52 and 96 °C (126 and 205 °F).
What is the minimum flash point of diesel?
| Fluids | Flashpoint [12] oF | Autoignition Temperature [13] oF |
|---|---|---|
| Diesel Fuel [ 1, 2, 3, 4] | 100-204 | 350-625 |
| Ethanol (in gasohol) [ 1, 3, 5] | 55 | 685 |
| Gasoline (50-100 octane) [ 1, 2] | -36 to -45 | 536-853 |
| Gasoline (unleaded) [ 4] | -45 | 495-833 |