University researchers are trying to find out whether footballers have got taller since the game was invented.
If proven it could lend weight to arguments for making goalposts bigger.
A joint study between the universities of Reading, South Australia and Ohio State is calling for fans to dig out football cards and stickers from before 1950 to help them collect more data.
It also hopes to discover if taller people have historically had a greater advantage at becoming footballers.
"Modern-day football is a global industry worth billions of pounds in revenue, yet it still uses laws on goal sizes drawn up in the mid-19th century," Prof Adrian Bell from the University of Reading said.
"We suspect footballers' body shapes have changed, with more emphasis on fitness and diet, as well as growth in average height in the general population.
"But up until now, this has never properly been studied among a representative sample of professional footballers."
Goalposts have remained 24ft (7.31m) wide by 8ft (2.44m) high in adult football since crossbars were made mandatory by the Football Association in 1882.
"Making goals bigger to increase the number of goals scored in matches has been a serious suggestion in recent years," said Dr James Reade, a sports economist from the University of Reading.
"Other rules have changed, so it's not inconceivable this might happen.
"If governing bodies do want to use changing player sizes as justification, it's important that decisions are based on solid data."
Fans can help the team gather more evidence of how players have potentially grown in stature between 1870 and 1950 by uploading copies of player cards and stickers.
"The more heights we collect, the clearer we'll be on whether players really have got taller, and by how much," Dr Reade said.
- To upload your football cards and stickers as part of the study - visit www.rdg.ac/playerheights